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Abstract

Congenital toxoplasmosis (CT) can result in visual impairment, hearing loss, serious neurologic sequelae and death in the infant. We studied the potential of the polymerase chain reaction (PCR) in cerebrospinal fluid (CSF) for diagnosis of congenital toxoplasmosis.For this purpose we studied both congenitally infected (diagnosed clinically and serologically) and non-infected infants born to untreated mothers.The infants ranged in age from 0 to 180 days. CSF PCR was positive in 27 of the 58 (46.5%) congenitally infected infants and was negative in each of the 103 infants without CT. The frequency of positive CSF PCR varied according to whether infants had major clinical signs of the disease; PCR was positive in 70.9%, 53.3% and 50.9% of those with hydrocephalus, cerebral calcifications and/or eye disease, respectively. Three of six infants who were negative for both IgM and IgA antibodies had a positive PCR in their CSF as the confirmatory test for diagnosis of congenital toxoplasmosis. IgM and IgA antibodies and CSF PCR, when combined, yielded a higher sensitivity for diagnosis of congenital toxoplasmosis when compared with the performance of each test alone.Our findings reveal that in infants with clinical and serologic findings suggestive of congenital toxoplasmosis and born to untreated mothers, CSF PCR has the potential to increase the frequency of cases in which the diagnosis is confirmed.

Abstract

Congenital toxoplasmosis can cause significant neurologic manifestations and other untoward sequelae.The Palo Alto Medical Foundation Toxoplasma Serology Laboratory database was searched for data on infants 0 to 180 days old, in whom congenital toxoplasmosis had been confirmed and who had been tested for Toxoplasma gondii-specific immunoglobulin G (IgG), IgM, and IgA antibodies, between 1991 and 2005. Their clinical findings were confirmed at the National Collaborative Chicago-based Congenital Toxoplasmosis Study center. We reviewed available clinical data and laboratory profiles of 164 infants with congenital toxoplasmosis whose mothers had not been treated for the parasite during gestation.One or more severe clinical manifestations of congenital toxoplasmosis were reported in 84% of the infants and included eye disease (92.2%), brain calcifications (79.6%), and hydrocephalus (67.7%). In 61.6% of the infants, eye disease, brain calcifications, and hydrocephalus were present concurrently. T. gondii-specific IgM, IgA, and IgE antibodies were demonstrable in 86.6%, 77.4%, and 40.2% of the infants, respectively. Testing for IgM and IgA antibodies increased the sensitivity of making the diagnosis of congenital toxoplasmosis to 93% compared with testing for IgM or IgA individually. IgM and IgA antibodies were still present in 43.9% of infants diagnosed between 1 and 6 months of life.Our study reveals that severe clinical signs of congenital toxoplasmosis including hydrocephalus, eye disease, or intracranial calcifications occurred in 85% infants whose sera were referred to our reference Toxoplasma Serology Laboratory during a period of 15 years. Laboratory tests, including serologic and polymerase chain reaction tests, were critical for diagnosis in the infants. Our results contrast remarkably with those of European investigators who rarely observe severe clinical signs in infants with congenital toxoplasmosis.

Abstract

Acute infection with Toxoplasma gondii during pregnancy and its potentially tragic outcome for the fetus and newborn continue to occur in the United States, as well as worldwide, despite the fact that it can be prevented. The infection can be acquired through ingestion of infected, undercooked meat or contaminated food or water. Transmission to the fetus occurs almost solely in women who acquire their primary infection during gestation and can result in visual and hearing loss, mental and psychomotor retardation, seizures, hematological abnormalities, hepatosplenomegaly, or death. Systematic education and serological screening of pregnant women are the most reliable and currently available strategies for the prevention, diagnosis, and early treatment of the infection in the offspring; this is largely because toxoplasmosis in pregnant women most often goes unrecognized. Treatment of the infection in the fetus and infant during the first year of life has been demonstrated to significantly improve the clinical outcome.

Abstract

The aim of this study was to determine the prevalence of toxoplasma antibodies among pregnant women in Cali, Colombia. In 2005, 955 pregnant women were tested for IgG and IgM antibodies and sociodemographic information was collected. Their average age was 25.1 years, overall IgG seroprevalence 45.8% (95% CI: 41.8%, 48.2%), IgM 2.8% (95% CI: 1.5%, 3.6%). Seroprevalence increased significantly with age, 39.0% in 14 to 19 years to 55.3% in 30 to 39 years (P = 0.001). There was a significant trend toward a higher seroprevalence in the lower socioeconomic strata (SES) (low: 49.0%, high: 29%, P = 0.004). The increase in seroprevalence by age was more significant in the lower socioeconomic strata (P = 0.002). Our results suggest a higher prevalence when compared with those of the national 1980 (33-37.6%) survey. In contrast to reports from other regions of the world, Cali has not seen a decrease in T. gondii seroprevalence over the past 25 years.

Abstract

Lymphadenopathy (LN) is the most common clinical manifestation of acute acquired toxoplasma infection in humans. The diagnosis of toxoplasmic lymphadenitis (TL) is established by serological methods and/or lymph node biopsy. In the United States, the differential agglutination (of acetone [AC]-fixed versus that of formalin [HS]-fixed tachyzoites) test (AC/HS test) has primarily been used in assessments of pregnant women as a component of the toxoplasma serological profile to distinguish between recently acquired infections and infections acquired in the distant past. We studied the AC/HS test in patients with TL to define its usefulness in diagnosing individuals presenting with LN and to determine its kinetics after the onset of LN. One hundred nine consecutive patients (158 serum samples) diagnosed serologically and by lymph node biopsy as having TL were studied. Specific patterns in the AC/HS test were noted to be dependent on the time from the clinical onset of LN (COLN). Acute AC/HS patterns were observed for more than 75% of patients who according to their histories had developed their TL within 6 months after COLN. Acute patterns were not observed beyond the 12th month except for a single patient for whom an acute pattern (400/800) persisted to the 13th month after COLN. Equivocal patterns were observed up to 36 months after COLN. Nonacute patterns were observed only for serum samples drawn at least 13 months after COLN. A nonacute pattern in an individual at less than 12 months after COLN should suggest an etiology other than TL. In such cases, investigation for alternative causes, including malignancy, should be instigated.

Use of a single serum sample for diagnosis of acute toxoplasmosis in pregnant women and other adultsJOURNAL OF CLINICAL MICROBIOLOGYPress, C., Montoya, J. G., Remington, J. S.2005; 43 (7): 3481-3483

Abstract

Using a single serum sample for testing for immunoglobulin G (IgG) Toxoplasma antibodies, differences in sensitivity of the dye test (which measures primarily IgG antibodies) and an IgG enzyme immunoassay were found useful for very early diagnosis of acute Toxoplasma gondii infection.

Abstract

Toxoplasmic lymphadenopathy (TL) is the most common clinical manifestation of acute acquired toxoplasma infection in normal individuals. The diagnosis is established by serologic methods and lymph node biopsy. Recently, tests for avidity of toxoplasma immunoglobulin G (IgG) antibodies have been introduced to help discriminate between recently acquired and distant infection with the parasite. We studied an avidity test to define the usefulness of this method and to determine the evolution of the IgG avidity in TL. Seventy-three consecutive patients diagnosed as having TL were studied. IgG avidity test titers were noted to be time dependent from the clinical onset of lymphadenopathy. Low IgG avidity test results were observed in patients who had developed lymphadenopathy from <1 month to 17 months prior to the sampling of sera, emphasizing that low IgG avidity test results are not reliable for diagnosis of recently acquired infection. In contrast, high IgG avidity test results were observed only in patients who had developed lymphadenopathy at least 4 months earlier. Thus, a high IgG avidity test result in an individual who has recent onset of lymphadenopathy (e.g., within 2 to 3 months of sera sampling) suggests a cause other than toxoplasmosis. In such cases, further workup is warranted in order to determine the cause of the lymphadenopathy.

Abstract

BALB/c are genetically resistant to development of toxoplasmic encephalitis (TE) when infected with Toxoplasma gondii, whereas CBA/Ca mice are susceptible. We compared TCR Vbeta chain usage in lymphocytes infiltrated into brains between these animals following infection. TCR Vbeta8(+) cells were the most frequent T cell population in brains of infected, resistant BALB/c mice, whereas TCR Vbeta6(+) T cells were more prevalent than Vbeta8(+) T cells in brains of infected, susceptible CBA/Ca mice. Adoptive transfer of Vbeta8(+) immune T cells, obtained from infected BALB/c mice, prevented development of TE and mortality in infected athymic nude mice that lack T cells. In contrast, adoptive transfer of Vbeta6(+) immune T cells did not prevent development of TE or mortality in the nude mice. The protective activity of Vbeta8(+) immune T cells was greater than that of the total Vbeta8(-) population. In addition, Vbeta8(+) immune T cells produced markedly greater amounts of IFN-gamma than did the Vbeta8(-) population after stimulation with tachyzoite lysate Ags in vitro. Thus, Vbeta8(+) T cells appear to play a crucial role in the genetic resistance of BALB/c mice against development of TE.

Abstract

Because congenital toxoplasmosis is almost solely the result of maternal infection acquired during gestation, it is critical to determine whether infection during pregnancy has occurred. In the United States, definitive diagnosis of the acute infection and the time of its occurrence have been compromised by a lack of systematic screening and the fact that only a single serum sample is submitted for testing. In studies in Europe, and depending on the method used, the demonstration of high-avidity immunoglobulin G (IgG) toxoplasma antibodies has been shown to exclude infection having occurred in the first 3 to 5 months of pregnancy. We investigated the usefulness of determining the avidity of IgG toxoplasma antibodies with a VIDAS kit (herein referred to as the VIDAS Toxo-IgG avidity kit, the VIDAS kit essentially rules out acute infection having occurred within the 4 prior months) in the setting of a reference serology laboratory in the United States. Sera (132 samples) from 132 women in the first 16 weeks of pregnancy were chosen because at least one test in the toxoplasma serological profile (TSP) suggested or was equivocal for a recently acquired infection. High-avidity antibodies were demonstrated in 75% of 99 sera positive with the IgM enzyme-linked immunosorbent assay (ELISA) and 31.3% of 16 sera with acute TSP results. A significant percentage of sera with equivocal results wtih the IgM ELISA or TSP also had high-avidity test results. Of 39 women for whom treatment with spiramycin had been suggested to attempt to prevent congenital transmission, 19 (48.7%) had high-avidity antibodies. These findings highlight the value of the VIDAS IgG avidity kit when used in combination with the TSP to exclude recent infection, especially when only a single serum sample is available.

Abstract

A total of 1073 infectious episodes (IEs) that occurred in 620 consecutive heart transplantation patients at Stanford Medical Center between 16 December 1980 and 30 June 1996 were reviewed. Infectious complications were a major cause of morbidity and mortality, second only to rejection as the cause of early deaths and the most common cause of late deaths. Of the IEs, 468 (43.6%) were caused by bacteria, 447 (41.7%) by viruses, 109 (10.2%) by fungi, 43 (4.0%) by Pneumocystis carinii, and 6 (0.6%) by protozoa. The largest number of IEs occurred in the lungs (301 [28.1%]). A significant reduction in the incidence of IEs and a delay in presentation after transplantation were observed; these were most likely related to the introduction of new chemoprophylactic regimens during the study period and prevention of significant disease caused by cytomegalovirus.

Abstract

A simple and efficient method using transgenic Toxoplasma gondii tachyzoites expressing beta-galactosidase was developed for detection of specific antibodies against the parasite in sera of patients. The titers obtained with the new test were similar to those obtained with the Sabin-Feldman dye test run in parallel. Although significant changes in endpoint titers were not observed when sera drawn sequentially at 2- to 3-week intervals were tested with both procedures, apparent differences in antibody affinity were observed with the new test which were not perceptible with the Sabin-Feldman dye test. Like the Sabin-Feldman dye test, the new test is based on complement lysis of tachyzoites, but it is much easier to perform and the reaction is read colorimetrically instead of visually.

Abstract

We examined the efficiency of detection of immunoglobulin M (IgM) antibodies to a 35-kDa antigen (P35) of Toxoplasma gondii for serodiagnosis of acute infection in pregnant women. A double-sandwich enzyme-linked immunosorbent assay (ELISA) with recombinant P35 antigen (P35-IgM-ELISA) was used for this purpose. On the basis of the clinical history and the combination of results from the toxoplasma serological profile (Sabin-Feldman dye test, conventional IgM and IgA ELISAs, and the differential agglutination test), the patients were classified into three groups: group I, status suggestive of recently acquired infection; group II, status suggestive of infection acquired in the distant past; group III, status suggestive of persisting IgM antibodies. Eighteen (90.0%) of 20 serum samples from group I patients were positive by the P35-IgM-ELISA, whereas none of the 33 serum samples from group II patients were positive. Only 4 (25.0%) of 16 serum samples from group III patients were positive by the P35-IgM-ELISA, whereas all these serum samples were positive by the conventional IgM ELISA. These results indicate that demonstration of IgM antibodies against P35 by the P35-IgM-ELISA is more specific for the acute stage of the infection than demonstration of IgM antibodies by the ELISA that uses a whole-lysate antigen preparation. Studies with sera obtained from four pregnant women who seroconverted (IgG and IgM antibodies) during pregnancy revealed that two of them became negative by the P35-IgM-ELISA between 4 and 6 months after seroconversion, whereas the conventional IgM ELISA titers remained highly positive. The P35-IgM-ELISA appears to be useful for differentiating recently acquired infection from those acquired in the distant past in pregnant women.

Abstract

Because fluoroquinolones have an immunomodulatory effect on cytokine production by lipopolysaccharide (LPS)-treated human monocytes, we examined the effect of fluoroquinolones on the survival of mice injected with a lethal dose of LPS. Trovafloxacin (100 mg/kg), ciprofloxacin (250 mg/kg), and tosufloxacin (100 mg/kg) protected 75% (P = 0.0001), 25% (P = 0.002), and 50% (P = 0.002), respectively, of mice against death. The fluoroquinolones significantly reduced serum levels of interleukin-6 and tumor necrosis factor alpha in LPS-treated mice. The protective effects of fluoroquinolones in LPS-induced shock in mice may also occur in humans.

Abstract

ABT-773 is active in vitro and in vivo against Toxoplasma gondii. It inhibited replication of RH strain tachyzoites in human foreskin fibroblasts. Mice infected intraperitoneally with tachyzoites and treated orally with 25, 50 or 100 mg/kg/day of ABT-773 for 10 days had 20% (P: = 0.016), 50% (P: = 0.003) and 100% (P: = 0.001) survival, respectively. Remarkable and highly significant survival was also noted in mice infected orally with strain C56 cysts and treated with ABT-773. Thus, ABT-773 may be useful for therapy of human toxoplasmosis.

Abstract

An enzyme-linked immunosorbent assay (ELISA) using four recombinant antigens of Toxoplasma gondii (rP22, rP25, rP29, and rP35) was used in an attempt to differentiate pregnant women with toxoplasma serologic profiles (TSPs) indicative of recently acquired infections (acute profile) from those with TSPs indicative of infections acquired in the distant past (chronic profile). In general, immunoglobulin G antibodies in sera from women with the acute profile reacted more strongly with the recombinant antigens than did those in sera from women with the chronic profile. However, reactivities differed significantly between antigens that reacted with a single serum and between sera that reacted with a single antigen. Because of these variations, we employed a combination of the four antigens in an ELISA (Comb-ELISA) and evaluated its ability to distinguish pregnant women with the acute profile from those with the chronic profile. Eighteen of 20 (90%) sera from acute-profile women were positive in the Comb-ELISA, whereas 69 of 70 (98.6%) sera from the chronic-profile women were negative. Thus, the Comb-ELISA may be useful for diagnosis of toxoplasmosis in pregnant women and for differentiation between recently acquired infections and infections acquired in the more distant past.

Abstract

The effect of the novel streptogramin antibiotic quinupristin/dalfopristin (synercid) on cytokine production in vitro was examined in monocytes obtained from healthy human volunteers and stimulated with either lipopolysaccharide or heat-killed Staphylococcus aureus (Pansorbin). Synercid at concentrations that are achievable in humans (1, 5, and 10 microgram/mL) significantly suppressed production of interleukin (IL)-1alpha, IL-1beta, IL-6, IL-10, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha in a concentration-dependent manner. Thus, synercid possesses significant immunomodulatory activity, in addition to its antimicrobial activity.

Abstract

The role of B cells in resistance against Toxoplasma gondii was studied using B cell-deficient (muMT) mice. Following peroral infection with 10 cysts of the ME49 strain, all muMT mice survived the acute stage of the infection but died between 3 and 4 wk after infection. In contrast, all control mice were alive at 8 wk after infection. At the stage during which muMT animals succumbed to the infection, parasite replication and pathology were most evident in their brains; small numbers of tachyzoites were also detectable in their lungs. Significantly greater numbers of T. gondii cysts and areas of inflammation associated with tachyzoites were observed in brains of muMT than in control mice. Large areas of necrosis associated with numerous tachyzoites were observed only in brains of muMT mice. Anti-T. gondii IgG Abs were detected only in sera of control mice, whereas similar levels of IFN-gamma were detected in sera of both strains of mice. Amounts of mRNA for IFN-gamma, IL-10, and inducible NO synthase in the brain did not differ between infected muMT and control mice. Expression of mRNA for TNF-alpha was increased in brains of muMT mice. Administration of polyclonal rabbit anti-T. gondii IgG Ab prevented early mortality and pathology associated with tachyzoites in the brain in the infected muMT mice. These results indicate that B cells play an important role, most likely through their production of specific Abs, in resistance to persistent active (tachyzoite) infection with T. gondii in mice, especially in the brain and lung.

Abstract

Because combination therapy is required to treat human toxoplasmosis, we examined combinations of the ketolides HMR 3004 and HMR 3647 with atovaquone, clindamycin or sulphadiazine in a murine model of toxoplasmosis. An oral dose of 50 mg/kg/day of HMR 3004 protected 30% of mice lethally infected with Toxoplasma gondii. The same dose protected 100% of infected mice when administered in combination with non-protective doses of atovaquone, clindamycin or sulphadiazine. Similar results were noted with 25 mg/kg/day of HMR 3647. These results demonstrate that these drug combinations are highly effective for treating toxoplasmosis in mice.

Abstract

We report a case of fatal central nervous system infection with Scedosporium apiospermum (Pseudallescheria boydii) in a heart transplant recipient. This ubiquitous fungus is known to cause mycetoma and localized infections in patients with otherwise normal conditions. Disseminated infections occur rarely and are seen primarily in patients who are receiving immunosuppressive medications or who have neutropenia. Often life-threatening when infection is disseminated and involves the central nervous system, this diagnosis is difficult to make rapidly because S. apiospermum (P. boydii) mimics Aspergillus spp. and Fusarium spp., both clinically and histopathologically. Imidazoles such as miconazole, but not amphotericin B, are considered the therapeutic compounds of choice. Improved diagnostic and treatment options are needed to optimize management of infections with S. apiospermum (P. boydii).

Abstract

The role of interleukin-6 (IL-6) in the pathogenesis of toxoplasmic encephalitis (TE) was examined by using IL-6-targeted mutant (IL-6(-/-)) mice. At 4 and 8 weeks after infection with the ME49 strain of Toxoplasma gondii, significantly greater numbers of T. gondii cysts and areas of inflammation associated with tachyzoites were observed in brains of IL-6(-/-) mice than in those of control mice. Large areas of necrosis were observed only in brains of IL-6(-/-) mice. Tachyzoites were frequently detected in the areas of necrosis, suggesting that necrosis was caused by proliferation of the parasite. These results indicate that IL-6 is protective against development of TE by preventing formation of T. gondii cysts and proliferation of tachyzoites in brains of infected mice. Whereas in brains of control mice, large numbers of inflammatory cells were always observed in areas where tachyzoites were detected, in brains of IL-6(-/-) mice, only small numbers of inflammatory cells were observed in many areas with tachyzoites. Lymphocyte preparations isolated from brains of infected control mice had significantly higher ratios of gamma/delta T cells and CD4+ alpha/beta T cells but lower ratios of CD8+ alpha/beta T cells compared to those of infected IL-6(-/-) mice. There were no differences in the ratios of these T-cell subsets in spleens between these mice. The amounts of mRNA for gamma interferon (IFN-gamma) detected by reverse transcriptase PCR were significantly smaller in brains of IL-6(-/-) mice than in those of control mice, whereas amounts of IL-10 mRNA were greater in the former than in the latter. IL-6 mRNA was detected only in infected control mice. The protective activity of IL-6 against development of TE appears to be through its ability to stimulate IFN-gamma production and induce infiltration and accumulation of different T-cell subsets in brains of infected mice.

Abstract

The capacity of interleukin 12 (IL-12) to potentiate drugs in the treatment of murine toxoplasmosis was examined. IL-12 (100 ng/injection), atovaquone (10 mg/kg of body weight/day), or clindamycin (5 mg/kg/day) administered alone caused delayed time to death or minimal survival rates. In contrast, significant survival rates resulted when the same dose of IL-12 was used in combination the same doses of atovaquone (P=0.01) or clindamycin (P=0.001). Infected mice treated with IL-12 plus drug produced significantly higher levels of gamma interferon than controls. Although IL-12 was effective only when administered before infection, these results suggest that this cytokine may be a useful adjunct in the therapy of human toxoplasmosis in situations when cysts reactivate and tachyzoites start multiplying in immunocompromised patients.

Macrolides, azalides, and streptogramins in treatment of opportunistic infections in immunocompromised patients3rd International Conference on the Macrolides, Azalides, and StreptograminsRemington, J. S.MARCEL DEKKER.1997: 189–204

Abstract

A case of pleuropulmonary tularemia was diagnosed by sputum culture and serologic studies in a patient who did not have classic epidemiological risks for tularemia. The patient had atypical pneumonia when initially seen and his condition slowly improved with antibiotic therapy that included erythromycin lactobionate. The diagnosis of tularemia was delayed because the gram-negative rod isolated from the patient's sputum was initially not speciated in an effort to reduce laboratory costs.

Abstract

Rifapentine, a derivative of rifamycin, was examined for its in vitro and in vivo activities against the protozoan parasite Toxoplasma gondii. The drug inhibited the intracellular replication of parasites and was not cytotoxic for the host cells at inhibitory concentrations. Mice infected either intraperitoneally with tachyzoites of the RH strain or orally with tissue cysts of the C56 strain were protected against death by treatment with rifapentine. The degree of protection was similar to that induced by atovaquone and apparently higher than that induced by rifabutin. Rifapentine may be a useful drug for the treatment of toxoplasmosis in immunocompromised individuals.

Abstract

Control of resistance to cyst burden following per-oral infection with Toxoplasma gondii has been mapped previously to a region of mouse chromosome 17 of approximately 140 kb. This region is contiguous with and contains the class I gene, Ld. Resistance to development of toxoplasmic encephalitis has also been reported to be controlled by genes in this region of H-2. TNF-alpha, D and L genes, as well as unidentified genes, are also in this region. The work described here was performed to identify definitively the gene(s) in this 140 kb region that confers resistance to cysts and encephalitis. The study demonstrates that relative resistance to T. gondii organisms and cyst burden in brain, and toxoplasmic encephalitis, 30 days following per-oral T. gondii infection is correlated absolutely with the presence of the Ld gene in inbred, recombinant, mutant and C3H.Ld transgenic mice. Mice with the Ld gene had lower cyst burdens and less encephalitis than those without the Ld gene. Specifically, 30 days after infection mice with the Ld gene had minimal perivascular inflammation and meningeal inflammation and very few Toxoplasma cysts or organisms in immunoperoxidase-stained preparations of their brains. Mice without the Ld gene had a similar pattern of inflammation, but in addition they had collections of inflammatory cells in the brain parenchyma. Free tachyzoites were found within these foci of inflammation and cysts were present in these areas as well as in contiguous areas without inflammatory cells. There were CD4+ and CD8+ T lymphocytes in the areas of inflammation and throughout the brain parenchyma. Mice that were resistant to cysts and encephalitis had little detectable brain cytokine mRNA expression, while mice that were susceptible had elevated levels of mRNA for a wide range of cytokines, consistent with their greater amounts of inflammation. The present work definitively demonstrates that a Ld-restricted response decreases the number of organisms and cysts within the brain and thereby limits toxoplasmic encephalitis and levels of interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), IL-6, IL-10, transforming growth factor-beta (TGF-beta), IL-1 alpha, IL1 beta and macrophage inhibiting protein (MIP) mRNA in the brain 30 days after per-oral infection.

Abstract

BALB/c mice develop toxoplasmic encephalitis (TE) but the pathology resolves; in contrast, CBA/Ca mice develop progressive TE. Immunohistochemical analysis revealed peak staining for interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF) in lymph nodes of both strains on day 7 of infection, with elevated levels of IFN-gamma and TNF persisting in CBA/Ca mice. TNF was present in the central nervous systems (CNS) of both strains of mice and correlated with severity of pathology. Interleukin (IL)-2 was detected in lymph nodes and CNS of CBA/Ca mice after day 52 of infection and only in the lymph nodes of BALB/c mice between days 14 and 21 after infection. Highest levels of IL-10 were observed in lymph nodes and CNS of infected CBA/Ca mice. Variations in cytokine levels in lymph nodes and CNS of these mouse strains may account for differences in their susceptibility to TE.

Abstract

Infection with Toxoplasma gondii is normally asymptomatic, but as a consequence of the AIDS epidemic the incidence of symptomatic disease and especially toxoplasmic encephalitis (TE) has grown in frequency. The high frequency of adverse reactions to conventional therapeutic regimens for toxoplasmosis highlight the need to develop new strategies for the management of this disease. The importance of cytokines in resistance against T. gondii has been shown primarily in murine models of toxoplasmosis and a number of cytokines (e.g., IFN-gamma, TNF-alpha, IL-2 and IL-12) have been proposed for trials in patients with TE. One mechanism by which these cytokines produce their effects is through stimulation of macrophages and/or NK cells. However, there are problems with immunological intervention in immunocompromised patients with TE since the infection is present primarily in the central nervous system (CNS), an immunoprivileged site, and because certain cytokines may down regulate the immune response. While much valuable information has been obtained from studies conducted in immunocompetent strains of mice their relevance to an immunocompromised host is unknown. The development of genetically altered mice with immune deficiencies offers promising new models that may allow for more rational development of new treatment regimens.

Abstract

The unusual occurrence, protein manifestations, and often devastating consequences of toxoplasmosis in patients with cancer emphasize the need for clinical acumen in the diagnosis and management of this disorder. Toxoplasmosis in patients with cancer has most commonly been described in association with Hodgkin's disease. It has also been reported, usually in the setting of treatment with antineoplastic agents, in patients with other lymphoproliferative disorders, hematologic malignancies, and solid tumors. In this review, among patients for whom the diagnosis was made early enough to begin specific treatment, conditions of 68% improved; this finding was in marked contrast to the severe morbidity and mortality observed for untreated individuals. The high mortality in the untreated group reflects the general debilitation and severe immunocompromise of these patients. Therefore, although toxoplasmosis contributed to a poor prognosis, it was not necessarily always the proximate cause of death.

Abstract

Levels of cytokine mRNA were studied in the central nervous system (CNS) of SCID mice infected with Toxoplasma gondii. This infection led to 100% mortality by day 23 postinfection. Inflammation was observed in the lungs on day 7 and in the heart, liver, and kidneys on days 14 and 18 of infection. In the CNS, necrotic, acellular lesions that contained numerous parasites, accompanied by a localized astrocyte activation, were evident on day 14. Polymerase chain reaction-assisted amplification of RNA revealed that, although transcripts for interleukin-1 alpha (IL-1 alpha) and IL-1 beta were present in the brains of uninfected mice, increased levels of these transcripts were detected on day 7 of infection. Transcripts for macrophage inflammatory protein 1 and transforming growth factor beta were also detected in brains of infected mice at this time point. On days 14 and 18, levels of these transcripts had increased and transcripts for IL-6, IL-10, gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF) were also detected. Transcripts for IL-2 or IL-4 were not detected at any of the time points. Detection of locally produced cytokine transcripts may reflect involvement of the cytokines in the immunopathogenesis of this infection or involvement in mediating antitoxoplasma activity. To assess the possible role of endogenous IFN-gamma, TNF-alpha, IL-10, IL-6, and GM-CSF, cytokine-neutralizing monoclonal antibodies were administered to infected SCID mice. Neutralization of IFN-gamma or TNF-alpha led to earlier mortality than that in controls. In contrast, treatment with antibody to IL-10 and IL-6 increased survival time. Treatment with anti-GM-CSF did not alter the time to death. These results indicate that TNF-alpha and IFN-gamma are both involved in T-cell-independent mechanisms of resistance to T. gondii in SCID mice and that IL-10 and IL-6 may downregulate the immune response to this pathogen.

Abstract

Recent advances in our understanding of the immunological mechanisms involved during infection with Toxoplasma gondii include evidence for the role of different subsets of lymphocytes and cytokines in acute infection as well as in reactivation of chronic infection. The mechanisms of presentation of T. gondii antigen have been clarified recently, and animal models of toxoplasmosis that mimic disease observed in AIDS patients developed.

Abstract

The purpose of this study was to characterize the epidemiologic, clinical, and laboratory parameters of a cohort of men at risk of AIDS-associated toxoplasmic encephalitis. One hundred seventeen (11%) of the 1,073 participants at the time of enrollment into the Chicago Multicenter AIDS Cohort Study (MACS) were seropositive for Toxoplasma antibodies. Significant differences in prevalence of antibodies between African-American, Hispanic, or white men were not observed (p = 0.49). One hundred one (86%) of the 117 antibody-positive participants had at least one follow-up serology performed and 6 (6%) of the 101 had a significant rise in IgG antibody titer on subsequent visits. Five of six participants with a significant rise in titer were also seropositive for HIV-1 at entry or seroconverted during the study. A trend toward higher IgG Toxoplasma titers and prevalence of IgM antibodies in participants seropositive for HIV-1 was observed, but the differences did not reach statistical significance. There was no evidence that the presence of Toxoplasma infection predisposed to development of CD4+ depletion or AIDS. None of the 183 individuals in the cohort who developed AIDS and who were seronegative for Toxoplasma antibodies developed toxoplasmic encephalitis. In contrast, of the 13 persons who developed AIDS and who were positive for Toxoplasma antibodies, 5 (38%) developed toxoplasmic encephalitis. Prevalence of Toxoplasma antibodies in the MACS population was independent of HIV-1 serostatus. Toxoplasma infection does not appear to predispose to progression of HIV-1 infection. The risk of development of toxoplasmic encephalitis in persons with AIDS and chronic Toxoplasma infection may have been underestimated by previous retrospective studies.

Abstract

A major cytoplasmic Toxoplasma gondii (T. gondii) antigen recognized by monoclonal antibody F3G3 (F3G3-Ag), as well as two surface antigens recognized by monoclonal antibodies 2G11 and 1E11 respectively (2G11-Ag; 1E11-Ag), were isolated from crude Toxoplasma sonicates using affinity chromatography. Purified F3G3-Ag induced long term protection against Toxoplasma infection in mice and induced Toxoplasma specific IgG antibody. CD4+ but not CD8+ T cells from immune animals proliferated and produced IL-2 upon restimulation with either Toxoplasma sonicate or F3G3-Ag in vitro. Furthermore, CD4+ T cells from mice immunized with F3G3-Ag responded to purified 2G11- and 1E11-Ag. In contrast, CD4+ T cells from mice immunized with 2G11-Ag responded to Toxoplasma sonicate and 2G11-Ag, but not to F3G3- or 1E11-Ag. The results may indicate that the protective F3G3-Ag shares immunogenic epitopes present also on 2G11- and 1E11-Ag, since the F3G3-Ag used for the vaccination did not contain detectable amounts of 2G11- or 1E11-Ag, and none of the antigens displayed any mitogenicity. Taken together the results show that the cytoplasmic F3G3-Ag of T. gondii induces CD4+ T helper cells, Toxoplasma specific IgG antibodies and long term protection against Toxoplasma infection, but does not induce detectable sensitization of the CD8+ T cell compartment.

THE ACTIVITY OF ATOVAQUONE-(566C80) IN MURINE TOXOPLASMOSIS IS MARKEDLY AUGMENTED WHEN USED IN COMBINATION WITH PYRIMETHAMINE OR SULFADIAZINEJOURNAL OF INFECTIOUS DISEASESAraujo, F. G., Lin, T., Remington, J. S.1993; 167 (2): 494-497

Abstract

The activity of atovaquone in the treatment of murine toxoplasmosis was greatly enhanced when administered in combination with pyrimethamine or sulfadiazine. Mice infected with lethal inocula of tachyzoites or cysts of Toxoplasma gondii and treated with doses of atovaquone, pyrimethamine, or sulfadiazine that were ineffective when administered alone had 70% survival when pyrimethamine plus atovaquone and 100% survival when sulfadiazine plus atovaquone was used. Of interest, doses of pyrimethamine and, particularly, sulfadiazine far below the doses that would induce any protection in infected mice were active when combined with atovaquone. These results suggest that clinical trials for treatment of toxoplasmosis in AIDS patients using the combination of atovaquone with sulfadiazine or pyrimethamine are justified.

Abstract

Studies were performed to determine whether CTL against Toxoplasma gondii-infected cells could be induced in a murine model of T. gondii infection in which CD8+ T lymphocytes have been shown to play a major role in resistance against this parasite. In 51Cr release assays, nylon wool nonadherent spleen cells from BALB/c (H-2d) mice immunized with the temperature-sensitive (ts-4) mutant strain of T. gondii were cytotoxic for T. gondii-infected P815 (H-2d) mastocytoma cells but not for uninfected cells. This cytotoxic activity was remarkably increased after in vitro stimulation with T. gondii-infected syngeneic spleen cells. The effector cells were shown to be CD8+ T lymphocytes, because the cytotoxicity was significantly inhibited by depletion of CD8+ T lymphocytes but not by depletion of CD4+ T lymphocytes. This cytotoxic activity was genetically restricted. Spleen cells from T. gondii-immune BALB/c mice were not cytotoxic for T. gondii-infected EL4 (H-2b) thymoma cells, whereas spleen cells from T. gondii-immune C57B1/6 (H-2b) mice were cytotoxic for T. gondii-infected EL4 cells but not for T. gondii-infected P815 cells. The cytolytic activity of CD8+ T lymphocytes against T. gondii-infected cells might be a mechanism whereby these cells confer resistance against T. gondii.

Abstract

Infection of pregnant women with Toxoplasma gondii places the developing fetus at risk for congenital infection. We report a prospective study of 43 documented cases of acute maternal Toxoplasma infections acquired during gestation in which the polymerase chain reaction (PCR) was evaluated for diagnosis of fetal infection and compared with the current standard methods. On the basis of direct lysis of pelleted amniotic fluid cells followed by amplification of a gene sequence specific for T. gondii, PCR correctly identified the presence of T. gondii in five of five samples of amniotic fluid from four proven cases of congenital infection. PCR also detected three of five positive cases from a nonprospective group. The two diagnostic methods of comparable speed, detection of specific immunoglobulin M from fetal blood and and inoculation of amniotic fluid into tissue culture, correctly identified only 3 and 4 of the 10 positive samples, respectively. The considerably more time-consuming methods of mouse inoculation of amniotic fluid and fetal blood both detected 7 of 10 positive samples. There were no false-positive diagnoses by any of the methods. Therefore, detection of T. gondii by PCR appears to be the most promising method for prenatal diagnosis of congenital Toxoplasma infection, since it is both extremely rapid and highly sensitive.

Abstract

At present, therapy for toxoplasmic encephalitis (TE) is the combination of pyrimethamine with sulfadiazine or trisulfapyrimidines. Unfortunately, due to adverse reactions to sulfonamides, many patients with acquired immunodeficiency syndrome (AIDS) are unable to receive a complete course of therapy. The promising results with clindamycin phosphate therapy in a mouse model of TE prompted us to seek further information about patients with AIDS with TE who had been treated with clindamycin. Fifteen such patients were identified in whom clindamycin was used to treat 18 episodes of TE. Eleven patients showed clinical or radiologic improvement after receiving clindamycin therapy, either alone or in combination with pyrimethamine. Twelve received oral clindamycin as suppressive therapy after discharge from the hospital. Adverse reactions possibly related to clindamycin therapy included diarrhea, reversible granulocytopenia, and skin reactions. The results of this retrospective study suggest that clindamycin, either alone or in combination with pyrimethamine, may represent an effective alternative therapy for TE in patients with AIDS. Whether this supposition can be substantiated by appropriately designed studies is presently being determined.